The invention relates to the use of a composition comprising a) 3,3′-methylenebis(5-methyloxazolidine) and b) one or more additives in the removal of sulphur compounds from process streams.
Hydrogen sulphide (H2S) is an unpleasantly smelling, toxic gas which is a great hazard to health and in industrial plants leads to severe corrosion phenomena. Legislators have therefore imposed strict obligations for decreasing the H2S content. Grotan® OX (3,3′-methylenebis(5-methyl oxazolidine), a water-free condensation product of formaldehyde and isopropanolamine in a molar ratio of 3:2) displays good effectiveness in the chemical neutralization of H2S.
WO 02/051968 A1 discloses a process for decreasing the amount of hydrogen sulphide in a liquid or a gas by treatment with an H2S-scavenging product. The H2S-scavenging product is obtained by reaction of i) a compound having a carbonyl group with ii) an alcohol, thiol, amide, thioamide, urea or thiourea. The product is preferably prepared by reacting formaldehyde with an amine-free alcohol or urea. An example of an amine-free alcohol is ethylene glycol. The H2S-scavenging agent can optionally be used together with amine, in particular monoethanolamine.
WO98/02501 discloses that bisoxazolidines can be used as scavenging agents for sulphhydryl compounds. An example of a bisoxazolidine is 3,3′-methylenebis(5-methyl oxazolidine), which is obtained by reaction of isopropanolamine with formaldehyde (in a molar ratio of 2:3). However, the scavenging action of 3,3′-methylenebis(5-methyl oxazolidine) (hereinafter MBO) for sulphur compounds is in need of improvement, especially in process streams having a low water content. Such process streams are frequently formulated on the basis of hydrocarbons.
According to DE 197 22 858 A1, compositions based on iodopropynylbutylcarbamate and formaldehyde depot compounds are used as preservatives. The addition of particular glycols, preferably 1,2-propylene glycol, has a positive effect on the odour of the compositions and reduces the emission of volatile materials (such as formaldehyde).
DE 102 44 442 A1 discloses a preservative which has a reduced formaldehyde emission and contains a) at least one formal and b) at least one emission-reducing additive selected from among urea, urea derivatives, amino acids, guanidine and guanidine derivatives.
The preservatives described in DE 10 2004 014 447 A1 comprise a) at least N-formal, b) at least one emission-reducing additive and c) monoethylene glycol.
DE 10 2012 203 003 A1 discloses a liquid preparation for reducing free oxygen and preserving water. The preparation comprises a) at least one N-formal and b) at least one dialkylhydroxylamine of the formula RR′NOH (where R and R′ are selected independently from among C1-C10-alkyl groups).